Conventionally, as this type of assistive apparatus, there is an already known apparatus disclosed in Japanese Patent Laid-Open No. 2003-220102 (hereinafter, referred to as “patent document 1”). The assistive apparatus of the patent document 1 includes moment generators on the hip joint, the knee joint, and the ankle joint of each leg of a person, with the moment generators connected to a foot supporting portion for supporting the foot of the person via beams. Moreover, it includes a sensor for detecting a force and moment acting between the foot supporting portion and the ground, a sensor for detecting a tilt angle of a beam, a sensor for detecting a force acting between the assistive apparatus and the person. On the basis of detected outputs of these sensors, a force to be generated by the each portion of the person is calculated when no support force (support torque) is applied by each moment generator, thereby causing each moment generator to generate a support force obtained by multiplying the calculated force by a certain reduction ratio. Thereby, the total load on the person is borne by the person and the assistive apparatus at a roughly predetermined ratio, so that the load on the person is reduced.
The apparatus of the patent document 1, however, calculates a force to be generated in each portion such as a joint of each leg by using the detected value of a force acting on the foot supporting portion of a landing leg when calculating a force to be generated in each portion of the person. Therefore, the calculated force is to be a force for supporting the total load of the person including the assistive apparatus. Therefore, even if the moment generator is caused to generate a certain rate of the calculated force as described above, the person makes a leg motion with being aware of the weight of the assistive apparatus attached to the person in a lot of situations during walking of the person. Consequently, the assistive apparatus easily causes a difference between an actual leg motion pattern and the motion pattern assumed by the person. Furthermore, it leads to causing an awkward leg motion or to making it hard for each moment generator to effectively generate a support torque, which enables a smooth leg motion.
As techniques for estimating joint moments to be generated in the joints of the legs during human walking, there have been known ones suggested by the present applicant, for example, in Japanese Patent Laid-Open No. 2003-89083 and Japanese Patent Laid-Open No. 2003-112893. The joint moments estimated using the techniques are necessary to support the total load of the person and the apparatus attached thereto. Therefore, even if the moment generators on the respective joints are caused to generate the predetermined rate of the joint moments calculated in these techniques, the same problem as the patent document 1 occurs.